The filters could be placed anywhere in the world, since carbon dioxide disperses throughout the atmosphere.
For all its appeal, the process is hideously inefficient. Carbon dioxide makes up less than 0.04% of the atmosphere, and removing climate-changing quantities of it requires filtering massive amounts of air.
Lackner calculated that sucking up all 28 billion tons of CO2 released worldwide each year would require spreading out his machines over a land area the size of Arizona.
That seems like a reasonable sacrifice to save civilization, until you consider the expense.
Experts estimate that it would cost up to $200 a ton to filter and store carbon dioxide from the air. That means the yearly vacuuming bill could reach $5.6 trillion.
Even filtering the greenhouse gas from smokestacks, where it is hundreds of times more concentrated and thus much cheaper to capture, is still deemed too expensive for commercial use.
The enormous cost raises the question: Who would pay?
It is the same impasse that has stymied efforts toward a global agreement to reduce emissions. China argues that the West should foot the bill because it created the problem over the last two centuries. The United States says China must accept its share of responsibility as the world's new top polluter.
The cost of the technology will surely fall over time, but without government action that is unlikely to happen soon enough to stave off the worst effects of climate change.
Without at least a 50% cut in emissions by mid-century, the United Nations' Intergovernmental Panel on Climate Change predicts that the temperature rise will exceed 2 degrees, resulting in worsening drought, a dangerous sea level rise and widespread extinction of species.
Paul Crutzen, a Nobel Prize-winning atmospheric chemist at the Max Planck Institute for Chemistry in Mainz, Germany, said that the failure to cut emissions might force the world to reshape the environment through drastic use of technology.
The risks could be enormous, but the risks of failing to reduce emissions could be greater, he said.
Crutzen said that only out of a "sense of despair" had he come to favor the last-ditch option of spewing more than a million tons of sulfur a year into the air.
It's a dirty proposition that, in some ways, is its own environmental crime. But it works, as shown by the 1991 Mt. Pinatubo eruption in the Philippines, which temporarily cooled the planet by almost 1 degree Fahrenheit. "It might be the last escape route from the problem," he said.
